Preheat your oven to 350°F (175°C) so it's ready for your gooey bars.
Line your 9x13 inch baking pan with parchment paper, allowing some overhang for easy lifting later.
In a large mixing bowl, whisk together the melted butter, granulated sugar, and brown sugar until smooth. Add in the eggs and vanilla extract, mixing until well combined.
In another bowl, whisk together the flour, baking soda, and salt. Gradually add the dry mixture to the wet ingredients, stirring until just combined.
Fold in the mini chocolate chips, ensuring they are evenly distributed throughout the dough.
Spread half of the cookie dough evenly into the bottom of the prepared pan. Press it down gently.
Place the Oreos in a single layer on top of the cookie dough, making sure they are evenly spaced.
In a small bowl, mix the sweetened condensed milk and the chocolate chips together. Pour this mixture over the layer of Oreos.
Spoon the remaining cookie dough over the chocolate chip and Oreos layer. It’s okay if some of the Oreos show through!
Bake in the preheated oven for 30-35 minutes, or until the edges are golden brown and the center is set.
Allow the gooey bars to cool in the pan for about 10 minutes before lifting them out using the parchment paper. Let them cool completely on a wire rack, then slice into squares and serve.
